Intersting quesion as thinking about it raised a few questions to me. Hope the devs can answer (see below).

I dont know anything about xplane, so no input from me there.FSX, as far as I know, basically uses this approach:- World- Heightmap, which basically gets smoothed a bit I guess- Landclass- Static textures based on Landclass/Slope of Terrain (with fake roads, etc)- Static Autogen Based on Texture- Vector data overlays (roads/rivers) - which is ugly as it cuts through textures- Anything custom placed (airports/buildings, etc)

Outerra, on the other hand, from what I understand:- Flat World- Heightmap- Procedural Processing of Heightmap to form Terrain, in order to fake Detail, eg. make it look more natural. This allows for detail down to submeter level (think little rocks). Also overhanging cliffs, etc. This is all based on probability calculations i think- Custom Terrain shaping layer- Landclass (not yet though? I think now everything is forestry green)- Procedural Ground textures, eg. grass blending with rock. No hard texture lines, right?- I guess custom Texture Injection (think Satelite imagery usage as ground textures - though this will look weird with later layers unless its marked for no procedural processing later on)?- Vector data (roads/rivers/rails/something else?)- Custom model placement after that I guess?- Procedural Calculation of object placement, based on landclass, vectors and Terrain. EG, is there a Tree here? Question, does this Calculation work in layers, and do subsequent calculations take into account the result of earlier calculations? Eg. If the city calculation yield at a housee of type h and position x/y, would a second pass take that into account, and place, for instance a tree or a pool near it?

Now the biggest question for me here is this. Procedural calcualtions (both for terrain and object placement) were explained on the blog as stepwise refinement calculations right? So the closer you are to area x/y the more refined the calculations get, and the more detail it can yield. Is this correct? For the object placement calculations, I think this could allow for insane detail, down to typical FPS detail? individual grass/stones. Mailboxes/garbage cans on streets. Is that all correct?

I don't have an in-depth knowledge of how is the world rendering implemented in XPlane, but I guess it's more or less comparable to FSX rendering.I think the fundamental difference between Outerra and FSX/Xplane is the procedural approach vs. the pre-made scenery. From what I've read, XPlane comes on 6 DVDs containing the meshes and scenery data, but still the resolution is relatively low (probably most visible in mountains).

Outerra uses elevation and climate data to generate terrain that can be continuously refined. Commenting on corona's post:- World = Flat World + Heightmap? Heightmaps data are processed into LOD layers, and below the finest heightmap level the fractal refiner kicks in and starts to generate the more detailed heightfields by fractal refinement process.

- Custom terrain shaping layer - not sure what's this

- Landclass - this will consist of rough (500m) raster based land class data processed in a way that allows for fractal refinement. Landclass data is used just as a kind of probability seed value to drive the refinement process, to achieve natural transitions. Also, this landclass will only include natural land types; civilization effect will be in a separate layer as vector data. This will also allow for continuous degradation - the return to the natural state.

- Vector data are actually applied after heightfield data are computed, before the ground materials are computed

- Model placement is manual, persistent, there's no autogen for this. It's more probable that it will work with specialized generators for vector defined areas - you'll specify area, assign a type (urban type x, pasture, field etc) so that a generator can create separate fields etc. Using OSM data where these regions are defined will be the priority. These vector overlays also modify/remove existing natural land type and vegetation maps.

With OSM data, or any vector data for that matter, we have to provide a city block generator that uses some parameters to create buildings and all objects there. For example, if there's an area designated as residential, separate plots should be cut, houses placed, with pools and gardens and everything - that's up to the generator. Originally there could have been a swamp land, but the overlay and generators will mod the land to a specific type.

As with the natural land generator, the generated detail level should depend on what detail is required, which mostly depends on the distance. Finer stages of the generators are invoked on more detailed tiles.Ultimately it should allow to generate insanely detailed procedural world, but always the separate generator stages could be switched off to override the procedural output. For example, the part that changes swampland to residential area can be on, but a particular parcel can be excluded from the later stages of the generator, so one can build a custom house there.

Darn, that sounds really nice. The one thing that outerra seems to have over them is their fractal generation to fill in detail where there is none in the source. Other than that, they sound very similar.

And...of course, jugding from the screenshots, they seem to already be considerable further along, especially concering city building. I'm still waiting daily for any news in that regard from our friends here ;-)

This will also allow for continuous degradation - the return to the natural state.

Sorry, I have to have you quantify this a bit. Does this mean that if an area is under-used, natural forces will take over? ie, grass, trees, etc, will completely obliterate the urban/suburban environment?

Very cool indeed, if I'm understanding you!

Logged

What we think, we become -- BuddhaThere is no spoon -- Neo, The MatrixThe Cosmos is all that is, or ever was, or ever will be. -- Carl SaganOuterra is all that is, or ever was, or ever will be. -- Me - Yes, I'm still around ... just been busy with other projects

And Austin's desire to use all available resources to calculate only 20 AI planes is not quite smart.

I really don't understand this point either, AI shouldn't be this cpu intensive. He also talks about how each plane will have fully realistic flight dynamics, which while cool (for watching them do crosswind landings) is completely overkill IMO, especially if ur doing it for all of them, while typically out of all the AI existing the player can see 3 max at any given time close enough to make any diff what so ever. Maybe that's where the 20 AI planes number comes from. But for a flightsim we're not talking 20 planes anyways, we are talking 10x times that at a minimum, and that shouldn't require a 20 core cpu either (BTW he keeps talking about the number of CPUs instead of CPU cores....which seems odd, or oldschool I guess).

Does this mean that if an area is under-used, natural forces will take over? ie, grass, trees, etc, will completely obliterate the urban/suburban environment?

I don't know yet how this turns out in the end, but the terrain materials are based on probability computation so that we can get natural looking lands. With artificial overlays you want sometimes a sharper blending with the surrounding terrain, but the blending can be also changeable. For example, if you have a wheatfield somewhere, it will be still recognizable after some years as it reseeds itself, but other vegetation will gradually creep in, choking the cultured strains of wheat etc. But even in a fresh field this process occurs.

Fractal blending uses a threshold parameter to derive what material/land type is where, and this parameter could be used to suppress artificial materials in a fractal manner - islands of impurities spreading outwards from seeds which have the highest inclination to deteriorate. Road surfaces require slightly different patterns than the fields though, and for buildings this would require specific support, but it's interesting concept nonetheless.